1. Field of the Invention
The present invention relates in general to an engine cooling system of the type wherein the coolant is boiled, so as to make use of the latent heat of vaporization thereof, and the coolant vapor used as vehicle removing heat from the engine, and more particularly to an improved arrangement of such system by which a radiator employed in the system is prevented from freezing even under very cold condition.
2. Description of the Prior art
Hitherto, a so-called "boiling liquid cooling system" (viz., evaporative cooling system) has been proposed for achieving cooling of an internal combustion engine. This type cooling system basically features an arrangmenet wherein a liquid coolant (for example, a mixture of water and antifreeze) in the coolant jacket of the engine is permitted to boil and the gaseous coolant thus produced is passed out to an air-cooled heat exchanger or radiator where the gaseous coolant is cooled or liquefied and then circulated back into the coolant jacket of the engine. Due to the effective heat exchange achieved between the gaseous coolant in the radiator and the atmosphere surrounding the radiator, the cooling system exhibits a very high performance.
However, as will become apparent as the description proceeds, some of the hitherto proposed cooling systems have suffered from the drawback that even when a mixture of water and antifreeze is used as the coolant, freezing of the coolant tends to occur in the radiator in cold seasons due to "localized coolant dilution phenomenon" occuring during operation of the system. Freezing of the coolant in the radiator deteriorates the performance of the cooling system and in a severer case, induces abnormally high pressure and thus abnormally high temperature in the coolant circulation system.